The influence of bond flexibility and molecular size on the chemically selective bonding of In2O and Ga2O on GaAs(001)-c(2×8)/(2×4)

Abstract

The surface structures formed upon deposition of In2O and Ga2O by molecular beam epitaxy onto the arsenic-rich GaAs(001)-c(2 x 8)/(2 x 4) surface have been studied using scanning tunneling microscopy and density functional theory. In2O initially bonds, with indium atoms bonding to second layer gallium atoms within the trough, and proceeds to insert into or between first layer arsenic dimer pairs. In contrast, Ga2O only inserts into or between arsenic dimer pairs due to chemical site constraints. The calculated energy needed to bend a Ga2O molecule approximately 70 degrees, so that it can fit into an arsenic dimer pair, is 0.6 eV less than that required for In2O. The greater flexibility of the Ga2O molecule causes its insertion site to be 0.77 eV more exothermic than the In2O insertion site. This result shows that although trends in the periodic table can be used to predict some surface reactions, small changes in atomic size can play a significant role in the chemistry of gas/surface reactions through the indirect effects of bond angle flexibility and bond length stiffness.

Scanning tunneling microscopy/spectroscopy study of atomic and electronic structures of In2O on InAs and In0.53Ga0.47As(001)-(4×2) surfaces

“…In 2 O 3 ͑s͒ sublimates as In 2 O ͑g͒ and O 2 ͑g͒ at 1000-1025°C. 26 However, due to the low sticking probability of O 2 on group III-rich ͑4 ϫ 2͒ surfaces, 24 the majority of the adsorbing species is In 2 O. In the experiment, a thermocouple is used to measure the sample temperature.…”

“…The bonding of In 2 O on group III-rich InGaAs͑001͒-͑4 ϫ 2͒ is quite distinct from the bonding of O 2 , In 2 O, and Ga 2 O on the As-rich GaAs͑001͒-͑2 ϫ 4͒ surfaces. 4,22,26 For O 2 chemisorption on GaAs͑001͒-͑2 ϫ 4͒, two O atoms break the As dimer bond and displace two As atoms on the row, which will create two undimerized As atoms with dangling bonds and indirectly pin the Fermi level. On the GaAs͑001͒-͑2 ϫ 4͒ surface, Ga 2 O molecules preferentially bond to As dimer rows and form Ga-As bonds.…”

Direct and indirect causes of Fermi level pinning at the SiO∕GaAs interface

“…These microscopic studies ͑Hale et al 17,18 and Negoro et al 19 ͒ have given insight into the atomic structures of adsorbates bound to the GaAs͑001͒-c͑2 ϫ 8͒ / ͑2 ϫ 4͒ surface and revealed that the cause of the Fermi level pinning was not excess As on the surface.…”

In-situ characterization of Ga2O passivation of In0.53Ga0.47As prior to high-k dielectric atomic layer deposition

“…As suggested previously, 21 the deposition of Ga 2 O on InGaAs and GaAs would ideally result in Ga 2 O units bonding to the As at the surface or on row edges. 19 This surface reaction should be difficult to detect using XPS with the As spectrum as this would manifest as As-Ga bonding at a nearly identical binding energy as that of the bulk As-Ga from the substrate.…”